How Seeding Works
Storm clouds are filled with super-cooled liquid water--droplets of water that are freezing-cold but don’t freeze.
In order for these droplets to rain or snow earthward, they must form ice crystals. To do this, they must grow extremely cold (minus 40 degrees Centigrade) or attach themselves to a solid particle. Nature sometimes provides such particles in the form of dust and pollution.
Cloud-seeders coax the process along by injecting silver iodide particles into the cloud. The super-cooled droplets freeze onto these particles, forming ice crystals, and precipitation begins.
That, in theory, is how cloud-seeding works.
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